Loopback

About: Loopback is a research topic. Over the lifetime, 1891 publications have been published within this topic receiving 14391 citations. The topic is also known as: loop-back.

On double-link failure recovery in WDM optical networks

Abstract: Network survivability is a crucial requirement in high-speed optical networks. Typical approaches of providing survivability have considered the failure of a single component such as a link or a node. We consider a failure model in which any two links in the network may fail in an arbitrary order. Three loopback methods of recovering from double-link failures are presented. The first two methods require the identification of the failed links, while the third one does not. However, precomputing the backup paths for the third method is more difficult than for the first two. A heuristic algorithm that pre-computes backup paths for links is presented. Numerical results comparing the performance of our algorithm with other approaches suggests that it is possible to achieve 100% recovery from double-link failures with a modest increase in backup capacity.

A single-chip dual-band 22-to-29GHz/77-to-81GHz BiCMOS transceiver for automotive radars

Abstract: Integration of multi-mode multi-band transceivers on a single chip will enable low-cost millimeter-wave systems for next-generation automotive radar sensors. The first dual-band millimeter-wave transceiver operating in the 22-29-GHz and 77-81-GHz short-range automotive radar bands is designed and implemented in 0.18-? m SiGe BiCMOS technology with fT/fmax of 200/180 GHz. The transceiver chip includes a dual-band low noise amplifier, a shared downconversion chain, dual-band pulse formers, power amplifiers, a dual-band frequency synthesizer and a high-speed highly-programmable baseband pulse generator. The transceiver achieves 35/31-dB receive gain, 4.5/8-dB double side-band noise figure, >60/30-dB cross-band isolation, -114/-100.4-dBc/Hz phase noise at 1-MHz offset, and 14.5/10.5-dBm transmit power in the 24/79-GHz bands. Radar functionality is also demonstrated using a loopback measurement. The 3.9 × 1.9-mm2 24/79-GHz transceiver chip consumes 0.51/0.615 W.

Full duplex digital transmission facility loop-back test, diagnostics and maintenance system

Abstract: A full duplex digital transmission, high-capacity digital, facility loop-back test, diagnostics and maintenance system having a digital transmission facility, transmission medium, and at least one microprocessor-based, full duplex facility loop-back diagnostics interface is located at predetermined end-user locations within the system. The system is capable of initiating a facility loop-back test and predetermined diagnostics for a predetermined digital transmission span and customer premises equipment at the location of the network interface for a specified end-user. The facility loop-back diagnostics interface has a performance monitoring mode of operation and a maintenance facility loop-back mode of operation. The diagnostics interface can be activated from a remote location and is compatible with and supports a particular protocol, specifically LAP-B protocol. The diagnostics interface has integral performance monitoring capabilities for nonintrusive multiple diagnostics testing and on-line monitoring of multiple predetermined performance characteristics for associated DS1 communications channels, or a specified DS1 communications channel, and customer premises equipment at the network interface. The microprocessor of the performance monitoring unit for the facility loop-back diagnostics interface is synchronized with an internal clock that is driven by conventional power. There is also a long-life battery for preventing historical performance data from being corrupted during a power loss. When the diagnostics interface is in the performance monitoring mode of operation, historical performance data pertaining to predetermined performance characteristics and criteria can be retrieved by utilizing the extended superframe, or superframe, embedded operations channel.

LIONS: An AWGR-Based Low-Latency Optical Switch for High-Performance Computing and Data Centers

Abstract: This paper discusses the architecture of an arrayed waveguide grating router (AWGR)-based low-latency interconnect optical network switch called LIONS, and its different loopback buffering schemes. A proof of concept is demonstrated with a 4 × 4 experimental testbed. A simulator was developed to model the LIONS architecture and was validated by comparing experimentally obtained statistics such as average end-to-end latency with the results produced by the simulator. Considering the complexity and cost in implementing loopback buffers in LIONS, we propose an all-optical negative acknowledgement (AO-NACK) architecture in order to remove the need for loopback buffers. Simulation results for LIONS with AO-NACK architecture and distributed loopback buffer architecture are compared with the performance of the flattened butterfly electrical switching network.

Ring transmission system

Abstract: A transmission system comprises nodes coupled in a ring via two multiplexed transmission paths having opposite transmission directions. The two paths can be time, space, or wavelength division multiplexed. Bidirectional communications between any two nodes are provided in normal operation using both paths around a first, most direct, part of the ring. In the event of a fault affecting such communications, a protection switch is made to maintain bidirectional communications between the two nodes using both paths around a second, remaining, part of the ring. In this manner, each path can simultaneously carry both normal and protection switched signals. In an embodiment of the invention, only the two nodes adjacent a fault need be aware of the fault, each of these nodes effecting a protection switch for signals terminated at the node and effecting a protective loopback for other signals needing protection. The invention enhances the total capacity of the paths for carrying normal and protection switched signals. A network may comprise a plurality of such ring transmission systems intersecting at at least one network node, the network node comprising a node of each ring and a cross connect switch for switching signals therebetween.